Char   Catalogue
  a    USNO-A1.0
  b    USNO-SA1.0
  c    USNO-A2.0
  d    USNO-SA2.0
  e    UCAC-1
  f    Tycho-1
  g    Tycho-2
  h    GSC-1.0
  i    GSC-1.1
  j    GSC-1.2
  k    GSC-2.2
  l    ACT
  m    GSC-ACT
  n    SDSS-DR8
  o    USNO-B1.0
  p    PPM
  q    UCAC-4
  r    UCAC-2
  s    USNO-B2.0
  t    PPMXL
  u    UCAC-3
  v    NOMAD
  w    CMC-14
  x    Hipparcos 2
  y    Hipparcos
  z    GSC (version unspecified)
  A    AC
  B    SAO 1984
  C    SAO
  D    AGK 3
  E    FK4
  F    ACRS
  G    Lick Gaspra Catalogue
  H    Ida93 Catalogue
  I    Perth 70
  J    COSMOS/UKST Southern Sky Catalogue
  K    Yale
  L    2MASS
  M    GSC-2.3
  N    SDSS-DR7
  O    SST-RC1
  P    MPOSC3
  Q    CMC-15
  R    SST-RC4
  S    URAT-1
  T    URAT-2
  U    Gaia-DR1
  V    Gaia-DR2
  W    Gaia-DR3
  X    Gaia-EDR3
  Y    UCAC-5
  Z    ATLAS-2
  0    IHW
  1    PS1-DR1
  2    PS1-DR2
  3    Gaia_Int  
  4    GZ
  5    USNO-UBAD
  6    Gaia2016
